La. Admin. Code tit. 33 § VII-803

Current through Register Vol. 50, No. 6, June 20, 2024

Section VII-803 - Subsurface Characterization

A. Boring Requirements

1. Boring Requirements Applicable to Type I, II, and III Facilities

a. Borings shall be installed and plugged and abandoned in accordance with the standards in this Chapter, as well as the guidelines established in the latest versions of the LDEQ's and Louisiana Department of Transportation and Development's (LDOTD's) Construction of Geotechnical Boreholes and Groundwater Monitoring Systems Handbook and the LDOTD's Water Well Rules, Regulations, and Standards in LAC 56. The administrative authority may approve other forms of geological investigation for Type III facilities, such as hand-augered borings, test pits, excavations, etc., provided that subsurface conditions are characterized by an individual who meets the requirements in LAC 33:VII.801.A, and any holes, test pits, etc., are properly plugged and abandoned.

b. Boring logs shall be submitted for each borehole, including boreholes for monitoring wells and piezometers, and shall include information for boring logs established in the latest versions of the LDEQ's and LDOTD's Construction of Geotechnical Boreholes and Groundwater Monitoring Systems Handbook and the LDOTD's Water Well Rules, Regulations, and Standards in LAC 56, including the ground surface elevation with respect to NGVD, lithology and the intervals that were cored continuously, and the depth of first encountered groundwater.

c. If the ground surface elevation has changed in any permitted area due to construction or other activities at the facility, than the affected borings shall be re-surveyed to reflect the current ground surface elevation.

d. A plan-view map shall be provided that shows existing topographic contours and locations of all borings, monitoring wells, and piezometers with respect to the facility.

e. A detailed plan-view drawing shall be provided that shows the proposed elevations of the base of units prior to installation of the liner system and boring locations.

2. Requirements Applicable to Type I and Type II Facilities

a. Geotechnical borehole spacing shall be no greater than 450 feet (minimum of four borings required) except for Type II landfarms that require a sufficient spacing between borings to adequately characterize the subsurface soils and groundwater conditions for the facility.

b. Existing permitted facilities that are planning a lateral and/or vertical expansion or changing the permitted lowest point of excavation within the permitted footprint may submit a work plan to the Office of Environmental Services to demonstrate that an alternative to the geotechnical borehole minimum spacing requirements set forth in Subparagraph A.2.a of this Section will achieve adequate characterization of the subsurface soils and groundwater conditions for the facility. The proposed alternative method shall include a demonstration that the subsurface soils and groundwater conditions have been adequately characterized or shall propose additional actions necessary to achieve adequate characterization. If the department concurs that adequate characterization has been performed, the spacing requirements of Subparagraph A.2.a of this Section may be waived.

c. The elevation (NGVD) of the lowest point of excavation shall be provided.

d. All boreholes shall extend to a depth of at least 30 feet below the elevation (NGVD) of the lowest point of excavation (or the lowest point of the zone of incorporation, for landfarms). At least 10 percent of the borings (minimum of three borings) shall extend to 100 feet below grade level to characterize the shallow geology.

e. All borings shall be continuously sampled to at least 30 feet below the elevation (NGVD) of the lowest point of excavation (or lowest point of the zone of incorporation, for landfarms), with the use of thin-wall and/or split-spoon devices or similar coring devices. After 30 feet, samples shall be at a maximum of 5-foot intervals. The Office of Environmental Services may approve other forms of boreholes logging on a case-by-case basis and with proper justification.

3. Boring Requirements Applicable to Type III Facilities

a. Type III facilities shall install a minimum of three borings and at least one boring for every 8 acres of regulated unit(s) to a minimum depth of 5 feet below the lowest point of excavation.

b. All borings shall be continuously sampled to at least 5 feet below the lowest point of excavation with the use of the administrative authority's approved form of geological investigation device.

c. Ground surface elevations (NGVD) of the boring location and the lowest point of excavation shall be surveyed or estimated through the use of USGS quadrangle maps.

d. Logs of borings and other forms of geological investigation approved by the administrative authority for Type III facilities shall be submitted on a geologic cross section and shall include applicable information required in Subparagraph C.2.a of this Section.

B. Groundwater Flow Determination Requirements Applicable to Type I and Type II Facilities

1. Groundwater flow directions shall be determined using a minimum of three piezometers or monitoring wells in each water-bearing zone including zones that comprise the uppermost aquifer and uppermost water-bearing permeable zone(s) (if present).

2. Piezometers and monitoring wells that are used to characterize groundwater flow directions shall be constructed, and well-completion diagrams submitted, in accordance with the applicable well construction standards in LAC 33:VII.805.A.3.

3. The reference point of each piezometer and monitoring well that is used for measuring water levels shall be surveyed by a professional surveyor, licensed in the state of Louisiana.

4. Water levels of piezometers and monitoring wells that are used for determining groundwater flow directions shall be measured at least four times in a one-year period (quarterly) to provide seasonal and temporal fluctuations in groundwater flow rates and directions.

C. Geology and Groundwater Flow Characterization Requirements Applicable to Type I and II Facilities

1. Regional Geology and Groundwater Flow Characterization

a. A geologic cross-section from available published information that depicts the stratigraphy to a depth of at least 200 feet below the ground surface shall be provided.

b. The areal extent, thickness, and depth to the upper surface, and any interconnection of aquifers, from all available information shall be provided for all recognized aquifers that have their upper surfaces within 200 feet of the ground surface.

c. The directions and rates of groundwater flow shall be provided for all recognized aquifers that have their upper surface within 200 feet of the ground surface, shown on potentiometric maps.

2. Facility Geology and Groundwater Flow Characterization

a. Geologic cross sections shall be provided for each transect (line of borings) and shall depict the following information in relation to NGVD:

i. lithologic and boring log data from all borings drilled at the facility, including borings for existing, as well as plugged and abandoned, monitoring wells and piezometers;

ii. locations and depths of borings, monitoring wells, and peizometers;

iii. excavation depths (or depths of the zone of incorporation, for landfarms) on applicable cross sections;

iv. screen intervals of all existing and plugged and abandoned monitoring wells and piezometers;

v. other applicable features such as faults, slurry walls, groundwater dewatering systems, etc.; and

vi. identification of individual stratigraphic units, including units that comprise the uppermost aquifer, uppermost water-bearing permeable zone(s) (if present), lower confining unit, and confining unit that underlies the uppermost water-bearing permeable zone(s) (if present).

b. The areal extent, depths, and thickness of all permeable zones to a depth of at least 30 feet below the lowest point of excavation (or zone of incorporation, for landfarms) shall be provided on structure contour maps and isopach maps, including the zones that comprise the uppermost aquifer and uppermost water-bearing permeable zone(s) (if present). Structure contour maps and isopach maps shall display the location of the facility, boring locations, and corresponding elevation or thickness measurement at each boring location.

c. The areal extent, depths, and thickness of the lower confining unit for the uppermost aquifer and the confining unit underlying the uppermost water-bearing permeable zone(s) (if present) shall be provided on structure contour maps and isopach maps. Structure contour maps and isopach maps shall display the location of the facility, boring locations, and corresponding elevation or thickness measurement at each boring location.

d. Any faults that are mapped as existing through the facility shall be displayed on structure contour maps and shall show the fault trace and arrows pointing to the downthrown side of fault.

e. At least four scaled potentiometric surface maps shall be provided over a one-year period (quarterly) for each saturated permeable zone to a depth of at least 30 feet below the lowest point of excavation (or zone of incorporation, for landfarms), including the zone that comprises the uppermost aquifer and uppermost water-bearing permeable zone(s) (if present). Scaled potentiometric surface maps shall display the location of the facility, monitoring well and piezometer locations, and corresponding water level elevation measurement at each well location.

f. Characterization of groundwater flow directions shall be provided between saturated permeable zones. The characterization shall include the use of various illustrations such as potentiometric surface maps, flow nets depicting vertical and horizontal flow directions, etc.

g. Discussion of any change in groundwater flow direction anticipated to result from any facility activities shall be provided.

h. Establishment of zones that comprise the uppermost aquifer, uppermost water-bearing permeable zone(s) (if present), and lower confining unit shall be provided.

i. Groundwater flow rates and calculations shall be provided for each zone that comprises the uppermost aquifer and uppermost water-bearing permeable zone(s) (if present).

La. Admin. Code tit. 33, § VII-803

Promulgated by the Department of Environmental Quality, Office of the Secretary, Legal Affairs Division, LR 33:1075 (June 2007), amended LR 33:2151 (October 2007).

AUTHORITY NOTE: Promulgated in accordance with R.S. 30:2001 et seq., and in particular R.S. 30:2154.